Conventionally, there are various power meters that measure motive power applied to a crankset for the purpose of measuring the efficiency of pedaling performed by a user, in connection with bicycles or cycling fitness machines.
For example, Patent Document 1 (WO 89/00401 A) discloses a device in which a gauge is suspended over a drive disk (spider) and a crank arm. By measuring the distortion occurring between the drive disk (spider) and the crank by the force applied to the crank by the pedaling operation of the user, the force (torque) used for the crank to rotate is measured.
Further, Patent Document 2 (WO 2008/058164 A) discloses a power meter according to two separate embodiments, in which a distortion gauge is provided at the spider arm or at the crank arm. The power meter in each embodiment measures the force (torque) used for the crank to rotate, by measuring the distortion occurring at the spider arm or the crank arm by the force provided to the crank via the pedal.
Still further, Patent Document 3 (U.S. Pat. No. 5,027,303) discloses a device in which distortion gauges are attached to the top and bottom faces of each of the right and left crank arms. The device measures the force (torque) used for the crank to rotate by measuring the distortion occurring at the crank arms by the force provided to the crank via the pedals.
As described above, all the power meters are identical to one another in that they are each structured to measure the force used for the crank to rotate by measuring the distortion occurring at the crank and the spider by the force provided to the crank via the pedal, using the distortion gauges provided at particular portions.